Evolution analysis of hemagglutinin gene of novel influenza virus A/H1N1 in 2009 pandemic / 第二军医大学学报

ABSTRACT

Objective: To investigate the evolutionary relationship of the hemagglutinin (HA) gene of novel influenza virus A/H1N1 in 2009 pandemic with the HA genes of A/H1N1 viruses isolated in different parts of the world previously. Methods: The sequences of the HA gene of the novel A/H1N1 strain and the reference sequences of human, swine, and avian influenza A viruses were retrieved from NCBI. MEGA 4.0 software was employed to align, blunt nucleotide sequences, and construct phylogenetic tree. The deduced amino acid sequences of the HA genes of novel influenza virus A/H1N1 were compared with those of the A/H1N1 isolates in North America, Europe, and Asia. Results: Phylogenetic tree of the HA genes of A/H1N1 strains worldwide showed that the HA genes of novel influenza virus A/H1N1 in 2009 shared a high homology with those of the 7 human A/H1N1 influenza viruses isolated in North America during 1976 to 2007, and shared a low homology with those of the human influenza viruses A/H1N1 isolated in Europe and Asia. Phylogenetic tree of the HA gene between different species showed that the HA genes of novel influenza virus A/H1N1 in 2009 had a close evolutionary relationship with those of the two swine A/H1N1 strains isolated in 1998 and 2007 in North America, but a distant evolutionary relationship with those of swine and avian A/H1N1 isolated in Europe and Asia. Alignment of amino acid at important antigenic sites showed that the HA gene of the novel A/H1N1 strains shared important antigen sites with the swine A/H1N1 influenza viruses isolated in North America, and did not share with the swine A/H1N1 influenza viruses isolated in Europe and Asia or the human A/H1N1 influenza vaccine strains. Conclusion: The HA genes of the novel influenza virus A/H1N1 might originate from swine A/H1N1 influenza viruses in North America after a long time evolution and the reassortment with fragments of human A/H1N1 in the area, and the current A/human/H1N1 influenza vaccine may not be effective for the novel A/H1N1 virus.